Motor vehicles include a powertrain that transmits torque to the driven wheels to propel the vehicle. The powertrain includes an engine and a transmission. The transmission is operable to change a speed ratio between an input connected to the engine and an output shaft connected to the driven wheels. The speed ratios are created by planetary gear sets disposed within the gear box. A series of clutches and brakes control the planetary gear sets to establish one or more power flow paths between the input and output shafts.
The transmission includes an associated gear shifter disposed within a passenger compartment of the vehicle. The gear shifter includes a plurality of positions such as PARK, REVERSE, NEUTRAL, and DRIVE. Movement of the gear shifter causes one or more of the clutches and brakes to engage or disengage placing the transmission in the desired state. When the gear shifter is in NEUTRAL, all of the controllable clutches of the transmission are disengaged to isolated the input and output shafts from each other.
Some transmissions include a neutral-idle operation in which the vehicle controller automatically places the vehicle in NEUTRAL when the vehicle is stopped with the brake pedal depressed and the gear shifter in DRIVE. Providing neutral-idle operation improves fuel economy by reducing the workload on the engine when the vehicle is stopped in gear. Some neutral-idle systems include a delay timer that inhibits neutral idle during stops of short duration.